1. Field of the Invention
The present invention relates to a fixing device provided in an image forming apparatus such as a printer, a copying machine, or a facsimile.
2. Description of Related Art
Examples of a fixing device provided in an image forming apparatus include one comprising an endless-shaped heating belt and a pressure roller pressed against the heating belt. Paper on which a toner image has been transferred is nipped by the heating belt and the pressure roller, to be heated and pressurized. Thus, the toner image is fixed on the paper.
The heating belt is stretched between a pair of rollers spaced a predetermined distance apart from and arranged parallel to each other in the direction of movement of the heating belt, as disclosed in Japanese Unexamined Patent Publication No. 2000-150112, for example. Each of the pair of rollers is supported so as to be rotatable by bearings arranged at both ends of the roller.
In the above-mentioned fixing device, it is desired that the heating belt is raised to a predetermined temperature in a short time period and power consumption is low. Therefore, the heat capacity of the fixing device is reduced by thinning the heating belt or shortening the perimeter of the heating belt, for example.
In the above-mentioned configuration, however, the bearings respectively arranged at the ends on each side of the rollers are arranged at the same position in the axial direction of the rollers. Generally, the diameter of the bearings for supporting the roller is larger than the diameter of the roller, so that a predetermined distance at which the bearings do not interfere with each other must be ensured between the pair of rollers. Consequently, there is a limit to shorten the perimeter of the heating belt stretched between the pair of rollers by reducing the distance between the pair of rollers. Therefore, the heat capacity of the fixing device cannot be reduced.